The purpose of the present study was to evaluate the correlations among expression of intercellular adhesion molecule 1 (ICAM-1) in glomeruli, levels of soluble ICAM-1 (sICAM-1) in sera, and renal injuries in patients with IgA nephropathy. The levels of sICAM-1 in sera from 27 patients with IgA nephropathy and 7 healthy controls were measured by the human soluble ICAM-1 immunoassay. The expression of ICAM-1 in glomeruli was detected by indirect immunofluorescence. We observed marked expression of ICAM-1 in glomerular capillary walls and mesangial areas in patients with advanced-stage, but not in those with mild IgA nephropathy. Since the histopathological changes in the advanced stage of this disease were characterized by diffuse mesangial cell proliferation and tubulointerstitial injury, the expression of ICAM-1 in the glomeruli may be of value in evaluating the degree of renal lesions in patients with IgA nephropathy. However, there was no significant change in the levels of serum sICAM-1 among mild-stage and advanced-stage patients and healthy controls. It appears that the measurement of serum sICAM-1 is not useful in evaluating the degree of renal injuries in patients with IgA nephropathy.